Dental cast trimmer



Dec. 18, 1934. r D L H LL 1,984,746

DENTAL CAST TR IMMER Filed Oct. 2, 1953 Patented Dec. 18, 1934 UNITEDVSTATES PATENT OFFICE Application October 2, 1933, Serial No. 691,897 4 Claims. (01. 164-41) This invention relates to a cutting implement and particularly to a trimmer for cutting, scraping and finishing casts or' models made of plaster of Paris, artificial stone, and like compositions, such as are commonly used by dentists, in the art of orthodontia, in the preparation of dentures, and in the construction of crown and bridgework.

Heretofore, it'has been common practice to remove the superfluous parts of the cast by means of a knife of the usual type. Owing to the hardness of the plaster, artificial stone, or other composition, a great deal of time and effort was consumed in leveling the base and cutting down the edges. Moreover, the knife was apt to slip, even when used by a skilled operator, and injuries have frequently resulted. 5

The'object of the present invention is-to provide an improved trimmer which will make possible the production of a cast having a superior finish, with a saving in time and effort, and without likelihood of injury to the operator.

A further object is to provide a trimmer which may be made at a low cost and which is characterized by simplicity of structure, as well as operation.

Other objects and advantages of the invention will be apparent from the following specification and drawing. In order that the invention may be clear to those skilled in the art, I have illustrated one embodiment of the invention in the accompanying drawing, in which Figure 1 is a view in perspective of the trimmer;

Figure 2 is a transverse vertical sectional view showing th manner of connecting the parts of the article; and

Figure 3 is a transverse vertical sectional view showing one position of the knife blade in a cutting operation.

Referring to the drawing by numerals, like numbers indicating like parts in the several views, 10 indicates a rectangular base, preferably formed of metal, which may be secured to a table or platform by means of the ears 11, integral with the base 10 and having apertures 12 to receive screws. The entire base 10 may be stamped from a sheet of metal or it may be formed from a solid block and two or more cars may be provided to secure the base in any convenient position.

A rectangular block 13, preferably of wood, is rigidly secured to the base 10 in any suitable manner, as by means of the screws 14. The block is somewhat shorter than the base 10 and it is positioned thereon so as to overlie the greater portion of the base, one end of the latter, however, remaining uncovered.

A metallic plate 15 is mounted on the end-of the base and secured by bolts 16 and nuts 17. An aperture, centrally located in the plate 15, is bounded by the annular flange 18, which projects upwardly from the plate and is curved inwardly. The aperture and the flange cooperate with a depression or concavity 19, provided in the base 10, to form a socket. A ball 20 works in the socket which follows the contour of the'ball far enough to prevent its escape. It will be observed that the socket is somewhat oversized with respect to the ball, thus permitting some degree of bodily movement of the ball with respect to the socket.

The ball 20 has integrally attached thereto a post 21 bifurcated at its upper end and the post may be tapered inwardly toward the ball at its lower. end to make possible a maximum freedom. of movement while at the same time; providing strength and rigidity.

A knife or cutting element 22, here shown as having a single cutting edge 23 and a handle 24, is pivotally supported at its end, between the arms 25 of the bifurcated post 21 by a bolt 26 which passes through opposite apertures in the arms 25 and a somewhat larger aperture 27 in the knife blade and is secured therein by a nut 28. The distance between the arms 25 is substantially greater than the thickness of the blade which passes between them, thus permitting a substantial lateral movement of the blade on the bolt 26. The handle of the knife is preferably dropped from the, line of the blade to facilitate handling of the knife.

The lower edge of the knife blade is cut away for a short distance, at the end which is pivotally connected to the post 21, the cutting edge 23 terminating in a shoulder 29.

The cut-away portion permits the blade to be moved longitudinally without being jammed or stopped by the bifurcation of the post 21. The cut-away portion, furthermore, permits of a relatively high point of bifurcation on the post 21 and consequently, greater rigidity.

The knife blade and handle are preferably relatively long in order that considerable leverage may be obtained, the bolt 25 acting as a fulcrum.

In operation, the cast to be trimmed is placed on the block 13 and is maintained in any suitable position, as shown in the drawing, Figures 1 and 3. The knife blade may then be swung downwardly about the pivot 26 with the blade vertical, or turned at any convenient angle to the vertical through which the bolt 26 passes.

to obtain either a shearing or a scraping action as desired.

The knife may be swung laterally with respect to the ball and socket and, because of the pivotal connection at the top of the post, may be raised to any desired angle with respect to the block. Furthermore, by twisting the handle, the knife may be bodily rocked or twisted and then moved in any plane.

The connection between the blade and the post to which it is pivoted permits of a further range of angular movement. The loose fit caused by the width of the slot between the arms 25 of the post 21, and by the enlarged aperture 27, enables the operator to obtain a greater angle of the blade with respect to the vertical plane than can be obtained by use of the ball and socket alone. Furthermore, the looseness of this connection permits the operator to lower the blade, along the vertical side of the cast, while the blade is tilted or twisted at an angle with respect to the longitudinal axis of the post, thus achieving a shaving or scraping action along a plane vertical to the block 13.

As the blade is brought down in the cutting action, it is sometimes desirable to give it a longitudinal, reciprocating, or sawing, motion in order to cut through the hard material more readily. This is permitted by the rotation of the ball about a horizontal axis as the operator moves the blade in a longitudinal direction.

The are which is described by the bolt 26, about the balland socket joint, as the cutting edge is moved longitudinally along the block 13, would tend to raise the edge slightly out of contact therewith were it not for the size of the aperture 27 Owing to the fact that the diameter of the aperture 27 is substantially greater than the diameter of the bolt 26, the latter moves upwardly without raising the blade in this operation.

From the above description, it will be obvious that the trimmer may be used to scrape, plane, or shear an object placed on the block 13 at nearly any angle by properly twisting or turning the handle. It will be apparent that curved surfaces may also be cut or finished, since the angle of incidence of the blade may be changed by the operator at will.

It will be understood that the invention is not limited to the details of construction shown in the drawing and that the phraseology employed in the specification is for the purpose of description and not of limitation.

I claim:

1. In a device of the class described, a cutting element and a base, the cutting element being connected to the base by a ball and socket joint, whereby cutting may be performed at various angles with respect to the base.

2. In a device of the class described, a base, a cutting element, a post connected at one end to the cutting element, the other end of the post being connected to the base by a ball and socket joint.

3. In a device of the class described, a cutting element, a base, and a post connecting one end of the cutting element to the base, the post being bifurcated at its upper end, the end of the cutting element being secured in the bifurcatedportion by a member passing through an oversized aperture in the cutting element, the knife being of less thickness than the space provided by the bifurcation.

l. In a device of the class described, a base provided with a socket, a cutting element, a post connected at one end to the cutting element, the other end of the post being provided with a ball fitted loosely in the socket for rotation and bodily movement therein.

DANIEL L. HALL. 

